A block of \(1\) kg is released from the top of a smooth curve \(\mathrm{AB},\) and then it encounters a rough surface \(\mathrm{BC},\) coming to rest at \(\mathrm{C}.\) The work done by friction is:
(take \(g=10\) m/s2)

1. \(25\) J 2. \(50\) J
3. \(-25\) J 4. \(-50\) J
Subtopic:  Work Energy Theorem |
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The work done by all the forces (external and internal) on a system equals the change in:

1. total energy 2. kinetic energy
3. potential energy 4. none of these
Subtopic:  Work Energy Theorem |
 76%
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A bullet from a gun is fired on a rectangular wooden block with velocity \(u\). When bullet travels \(24\) cm through the block along its length horizontally, velocity of bullet becomes \(u/3\). Then it further penetrates into the block in the same direction before coming to rest exactly at the other end of the block. The total length of the block is:
1. \(30\) cm
2. \(27\) cm
3. \(24\) cm
4. \(28\) cm
Subtopic:  Work Energy Theorem |
 68%
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NEET - 2023
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A body of mass \(1\) kg is thrown upwards with a velocity \(20\) ms-1. It momentarily comes to rest after attaining a height of \(18\) m. How much energy is lost due to air friction?
(Take \(g=10\) ms-2)
1. \(20\) J
2. \(30\) J
3. \(40\) J
4. \(10\) J

Subtopic:  Work Energy Theorem |
 87%
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AIPMT - 2009
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A bicyclist comes to a skidding stop in \(10\) m. During this process, the force on the bicycle due to the road is \(200\) N is directly opposed to the motion. The work done by the cycle on the road is:

1. \(+2000\) J 2. \(-200\) J
3. zero 4. \(-20000\) J
Subtopic:  Work done by constant force |
 58%
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The work done by gravity on a projectile of mass \(m\) fired with a speed \(u\) at an angle \(\theta\) to the horizontal, until the time of impact is:
          
1. zero 2. \(-\frac12mu^2cos^2\theta\)
3. \(-\frac12mu^2sin^2\theta\) 4. \(-\frac12mu^2\)
Subtopic:  Work done by constant force |
 60%
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A force of \(100\) N acts on a block, always acting opposite to its velocity. The block moves from \(x=4\) m to \(x=10\) m and then to \(x=6\) m. The work done by the force is:
1.  \(200\) J
2.  \(-200\) J
3.  \(1000\) J
4.  \(-1000\) J
Subtopic:  Work done by constant force |
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A body of mass \(0.5~\text{kg}\) travels in a straight line with velocity \(v=ax^{3/2}\) where \(a=5~\text{m}^{-1/2}\text{s}^{-1}\). The work done by the net force during its displacement from \(x=0~\text{m}\) to \(x=2~\text{m}\) is:
1. \(15~\text{J}\)
2. \(50~\text{J}\)
3. \(10~\text{J}\)
4. \(100~\text{J}\)

Subtopic:  Work Done by Variable Force |
 67%
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In a ballistics demonstration, a police officer fires a bullet of mass \(50.0\) g with speed \(200\) m/s on soft plywood of thickness \(2.00\) cm. The bullet emerges with only \(\text{10%}\) of its initial kinetic energy. The emergent speed of the bullet is:

1. \(0\) 2. \(53.2\) m/s
3. \(63.2\) m/s 4. \(6.32\) m/s
Subtopic:  Work Energy Theorem |
 67%
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A horizontal force \(F\) acts on a \(2\) kg block placed on a smooth horizontal plane. It varies with time \(t\) as shown in the figure. The block is initially at rest.
           
The work done by the force until \(t=2\) s, equals:
1. \(6.25 \) J
2. \(4.5 \) J
3. \(2.25 \) J
4. \(1.5\) J
Subtopic:  Work Done by Variable Force |
 63%
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